The present application relates to a battery pack including a non-aqueous electrolyte secondary battery and a method for producing the same. More specifically, the present application relates to a battery pack including a battery and a protection circuit board which are integrated into a single device with a covering material and, wherein the battery includes a battery element covered with a packaging member, wherein the battery element includes a positive electrode and a negative electrode which are spirally wound together or stacked on one another through a separator, and a method for producing the same.
In recent years, various types of portable electronic devices, such as camera-integrated video tape recorders, cellular phones, and laptop computers, came on the market, and those having smaller size and weight are being developed. As the portable electronic devices are reduced in size and weight, a battery pack used as a portable power source for the electronic devices is required to have increased energy and reduced size and weight. As an example of the battery used in such a battery pack, there can be mentioned a lithium-ion secondary battery having a high capacity.
The lithium-ion secondary battery includes a battery element having a positive electrode and a negative electrode capable of being doped and dedoped with a lithium ion, wherein the battery element is sealed in a metallic can or a metal laminated film and controlled by a circuit board electrically connected to the battery element.
Some known lithium-ion secondary batteries constitute a battery pack including a battery element sealed in a metallic can or a metal laminated film and a circuit board, which are contained in a casing having upper and lower spaces divided (see, for example, Patent documents 1 to 3).
[Patent document 1] Japanese Patent No. 3556875
[Patent document 2] Japanese Patent No. 3614767
[Patent document 3] Japanese Patent No. 3643792
Among the known lithium-ion secondary batteries described above, the battery having a battery element sealed in a metallic can easily achieve a high dimensional accuracy, but this battery has a problem in that the thickness or weight of the battery is likely to be increased.
On the other hand, the battery having a battery element sealed in a metal laminated film is small in thickness and weight, as compared to the battery using a metallic can, but this battery has problems in that the size of the battery element largely varies and hence it is difficult to improve the dimensional accuracy of battery, and that the mechanical strength of battery is low.
In a known battery pack having a lithium-ion secondary battery which includes a battery element sealed in a metallic can or a metal laminated film, and a circuit board contained in a casing, for protecting the battery and circuit board from an external impact and the like, it is required that the casing has a satisfactory thickness. Further, in bonding together the upper and lower divided casings using an adhesive double-coated tape or by ultrasonic welding, the casings require a satisfactory thickness for facilitating the bonding of them, and the whole of the battery pack is inevitably increased in thickness or weight, and this battery pack has a problem in that it is unsuitable for portable power source.